No, there is no need to do it for this reason. There are many other good reasons to build habitats in space and to have some humans in space at least. But this is not a good reason for it. Let me explain why.
So many people say we are doomed, and have to become "multiplanetary" to escape that doom. But if you look at it carefully - we aren't at all!
Global warming at its worst will increase the temperature of Earth by a few degrees. We absolutely have to stop that and we can. It will cause mass extinctions if this happens because many plants and animals can only live in limited habitats. Species in tropical jungles go extinct if you change the temperature of the jungle by a few degrees. If the oceans go just a bit acid, then corals go extinct, as has happened many times in the geological past. If the temperature rises just a little, then trees will no longer be able to grow where they are and as trees can't walk, that means that many will go extinct also.
But there is no way this will make humans extinct. We are far more adaptable than these species. There are humans in tropical jungles and in the Arctic, and they are able to survive with only the most rudimentary of technology in these places.
We don't need to worry about safeguarding the future of our species because of global warming.
Earth is not even particularly warm at present. It's actually geologically in an "ice age" - a period when the Earth has land masses or enclosed seas at one or other - or in our case both of the poles. For most of its history, the poles were open ocean, and there was no permanent ice anywhere at sea level and the Earth as a whole was much warmer (ice reflects heat away into space and cools down the planet).
The dinosaurs lived in a much warmer planet than the one we live in. So global warming is not at any risk of making Earth unusually warm. Indeed, it may have prevented us from going into an ice age in the near future. It's harmful for us because it is happening so quickly and because so many species are sensitive to tiny changes of temperature of a few degrees, and because of the sea level rises, the changes of climate such as storms, drought, flooding, more extremes of both cold and hot that are predicted to happen as the temperature of the Earth rises slightly. Nothing there that would make us extinct.
And also - asteroid impacts won't make us extinct. The impact that made the dinosaurs extinct was survived by turtles, birds, even the dawn redwood.
This turtle briefly ruled the world after the dinosaurs were wiped out
And this tree
survived the dinosaur extinction and is still growing today, the Metasequoia
As well as the avian dinosaurs.
And crocodiles and alligators Survivors
With our technology, even the most rudimentary technology such as boats, able to dig mines and build shelters, we are more versatile than any of those, and many humans would surely survive a similar event.
And the chance of it is tiny. Only one chance in ten million for the next century, and we are doing surveys that would give us decades of warning once they are complete for most asteroids. And can deflect them also especially with lots of warning.
And we can't be hit by a really large asteroid large enough to boil the Earth's oceans and remove its atmosphere. There were many such asteroids in the early solar system but the late heavy bombardment finished more than three billion years ago, and Jupiter is protecting us from them now, apart from the ones in the asteroid belt which are in stable orbits at least over periods of millions of years. We can confirm this from the cratering record in the inner solar system, that we aren't at risk at all from really huge asteroids, only the smaller ten kilometer or so ones like the one that made the dinosaurs extinct.
And then - there is nowhere in space that is remotely as habitable as Earth.
If something did happen to make humans extinct on Earth, or nearly extinct, and you had anyone, anywhere in the solar system who survived the disaster - where do you think they would want to go to set up home and rebuild after the disaster? Earth. Mars or the Moon?
So where is the best place for the backup?
We could build backups on Earth far more easily than anywhere else. And it doesn't make much sense to have the backup on the Moon or Mars when it is needed for Earth to recover after a disaster. There would be many humans left on Earth, and what use is it to them to have a technological habitat somewhere on the Mars or the Moon? Anyone living there would have far worse chance of survival than people on Earth because here, after all, no matter what, we can breath the air. And have water, and a moderate temperature ideal for us, and protection from cosmic radiation.
And we can build houses here easily, from bricks, wood, indeed at a push you can sleep out of doors especially in the warmer parts of the world. Even in colder places, all you need in most parts of the world is a decent sleeping bag and a tent, and you could survive almost anywhere, if you can find enough food and water. Or if you can find wood, you can light a fire to keep warm.
No need to don a spacesuit, pressurized, stiff gloves, hard to work in, to make a highly technological habitat that needs computers to run it, and lots of machines, and if they go wrong you have had it. And your habitat pressurized with ten tons per square meter of outwards pressure - and the only way to keep warm again is to use highly technological machinery.
At least in the near future. Further into the future maybe we can build space colonies that have economies of scale. But even then - it's going to be hard to beat the Earth where you don't even need to build a habitat at all to have oxygen to breath, food to eat, wood to burn if necessary, to stay alive.
I think there are many good reasons for having humans in space. Much like the reasons there are for exploring Antarctica in the nineteenth century, then setting up bases there.
But I don't think myself that they are good places to colonize. And I think that the idea of making this a priority would divert attention away from the very valuable but more limited settlement we can do in space, doing things that are of direct value to the Earth as well as things that benefit us scientifically, and learning about our solar system and the origins of life.
I think we need to acknowledge that we are a young species. Only had space technology for less than a century. We live in a solar system with one beautiful habitable planet our Earth. And our priority should be to keep it that way. Whether we do anything else in the future, there is no hurry. If we can keep our Earth in good condition we have millions of years ahead of us to decide what to do next.
One thing we can do with our technology is to detect and divert asteroids that may be a future threat to Earth. We may be able to mine useful resources in space. We may be able to get solar power. We may be able to do many things. Exciting, valuable, useful things we may be able to do.
I'm moderate in my views about space settlement. I think it is neither good nor bad, but can go either way.
If we go into space with the idea that protecting our home planet is of the highest importance - I think we are more likely to survive than if we go into space with the aim to try to become multiplanetary because we think our home world is potentially doomed.
Especially when our home planet is not threatened by any extinction causing disaster.
Of course if our home world was indeed threatened because our sun is about to go supernova, or there's a planet sized asteroid headed our way - that's a very different story :).
But for us, in a relatively quiet area of the galaxy, far from the galactic core, in orbit around a stable star, not prone to extreme solar flares, not one that goes supernova, no nearby stars of the type that can go supernova - I see protecting our home planet from natural disaster as a top priority.
An ET might be quite bemused at the way we have so many rockets and spy satellites pointed at each other and so little by way of space technology facing outwards, to detect asteroids or deflect them. So many huge spy telescopes pointed at Earth. on secret military missions. Almost nothing looking outwards, just Hubble of the really large space telescopes, then in the future the James Webb telescope.
Compared to the amount of technology we have facing towards the Earth treating each other as the threat to be neutralized, the amount devoted to planetary protection is absolutely minute.
Our government in the UK is currently contemplating spending probably $100 billion on renewing Trident, submarines armed with nuclear missiles of no use at all except for "mutually assured destruction".
With that money just the UK on its own, a fairly small country in the world as a whole - quite wealthy but there are many countries more wealthy - we could easily build 200 copies of the B612 telescope, orbiting between Earth and Venus, looking out for Near Earth asteroids in the infrared, especially the hard to detect ones between us and the sun.
Just one such telescope would find nearly all the medium sized to small NEOs within 6.5 years, and make a good stab at finding the 20 meter ones as well. Think what we could do if we all got together to work to find them all, world wide, putting even a tiny fraction of our defense budgets behind the project?
I think we should do things like that with our space technology. Plus support the Earth in all the ways we can. And also explore the solar system, but acknowledging our lack of knowledge and limitations, so with humility. Taking care, that we don't repeat the many mistakes we have made on the Earth as we explore our solar system.
So - no, I don't think we should focus on colonization. We should focus on space exploration, discovery, and have humans in space for what they are good at. With the robots as our mobile eyes and hands and ears in the solar system. I see a future of collaboration between humans and robots in space, with both doing what they do best. Robots can stay patiently in one spot on the Moon or Mars fed by only a trickle of electricity from solar panels, for days, weeks, months, years just exploring one tiny spot. No need for food. No need for oxygen. Can be sterilized for search for life or prebiotic organics - humans can never be sterilized of microbes in the way a robot can be. And a few humans could control dozens of robots like that, hop about in virtual reality from one spot to another. A bit like the game of civilization. I think that's a quite likely future in space. Just because space is so inhospitable to humans, a bit like the sea bed. Humans can go to the sea floor, but especially for deeper places, then it makes more sense to send robots. Less danger, more capable, and same thing, they can stay there for weeks or months or even years on end, which humans could never do without a huge logistics problem.
Depends. Maybe we will find some way to build closed systems that work in space. But remember - if that happens, it will also be possible on Earth. And far easier to build a habitat in a desert, in an atmosphere where you can breath the air, with nitrogen in the atmosphere, and water vapour in huge quantities even in our driest deserts - and even the Sahara sand has a reasonable percentage of water.
If the Sahara was another planet, a planet with an Earth atmosphere, covered in Sahara desert, nothing else there at all - and same temperature, you'd look at it and say "wow, how habitable this is, nearly as habitable as Earth!". It would be far far far more habitable than Mars. Even without the seas we have on Earth.
So if we ever build this technology the space colonists talk about and assume for the future, we could use the same technology to green the deserts of Earth for far less cost.
As for the idea of going into space out of fear that we will destroy ourselves through technology - well if we ever send millions of people into space with spaceships - if flights into space get as commonplace as present day flights to other continents - well that's a double edged sword. It would have to be a far more peaceful future than we have now, as that would mean you have millions of people with easy access to far more than ICBM level technology. Indeed a big drive to colonize space, if it ever lead to warfare and conflict between the colonists and each other or with Earth could be the very thing that makes us extinct, if anything could.
Which is why I see it as neutral. Go into space with the right attitude, with keeping Earth safe as our priority, and I think we've got a decent chance. So I think that should be our focus, not colonization. At this stage anyway, until we know more about our solar system, our galaxy and ourselves.
Longer term, yes, Earth is threatened. A half billion years from now. But that's a future so far away that humans could evolve a second time all the way from the most primitive multicellular creatures. That's nearly twice the length of time the trilobites lasted on Earth - amongst the longest surviving groups of creatures ever to have evolved on Earth. We would need to be a longer lived species than trilobites for that to be of relevance to humans.
I know that Carl Sagan argued strongly for colonization in his Pale Blue Dot. He was putting forward a carefully considered scientific and philosophical and ethical argument. But astronomy has moved on a lot since he wrote "Pale Blue Dot". At the time we didn't have an accurate picture of the impact risk for Earth. And he was also writing at a time wehn the prevailing scientific belief was that there is no other life in our solar system. Nowadays many astrobiologists would almost trend in the opposite direction to say that present day life is possible, even likely. And scientific knowledge has moved on in many other ways also.
He was certainly arguing for our species to settle other worlds in Pale Blue Dot - but he also presents a case based on various arguments he set out as a scientist. And made clear his case depends on those arguments. Which makes it something we can reassess.
It's a different situation now. And no, I don't think we need to focus on colonization as a priority, not at present. I think we need to focus instead on exploration, discovery, and protecting Earth.
And that our top priority should be the health of our beautiful planet Earth.
See also my science20 blog posts:
End Of All Life On Earth - A Billion Years From Now - Can It Be Avoided - And Who Will Be Here Then?
Why We Can't "Backup Earth" On Mars, The Moon, Or Anywhere Else In Our Solar System
Ten reasons not to live on Mars great place to explore
Could Astronauts Get All Their Oxygen From Algae Or Plants? And Their Food Also?
Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them
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